As a method for interfacing RF input/output signals in a communication device with each other, a SMA type connector, an N type connector, a DIN type connector and the like are widely used. Usually, one of such common connectors is selectively used in consideration of the size and the RF output power. Since the SMA type has a small size, it occupies less space and it is easily fastened even in a narrow space. However, it has a problem of bad inter-modulation distortion characteristics (hereinafter, referred to as PIM). Meanwhile, the N-type has excellent PIM characteristics, but since it has a larger size than the SMA type, it will occupy a lot of space, and there is also a need to spend a wider space for tightening. Although the DIN type also has the most excellent PIM characteristics, the spatial utilization is not further easier due to an increase in size as much.
Since the environment that requires the PIM characteristics further increases with an increase in the frequency of use, in order to satisfy these PIM characteristics, it is the right choice to use the DIN type. However, it has a problem that occupies a lot of space as described above. Also, as decreases in the weight/size of the communication devices progress, spatial issues caused by conventional thread-fastening type connectors have become more sensitive matters, and have caused inconveniences to be used on the user side.
In addition to the PIM characteristics, as the factors that become restrictions on the use of the plug-in connector, there are isolation characteristics and the like. For example, in an ICS repeater, the interference between the forward and reverse signals generated in the apparatus gives a very sensitive affect on the ICS performance of the device. However, in the case of the plug-in connector, since the isolation characteristics are greatly lower than the thread-fastening type connector, for some of the connections between modules, there are restrictions on the application, and thus, it has not been possible to solve the spatial problems and the inconvenience for use.